Crash safety is an important and much discussed area in the development of modern cars. Attempts at improving passenger safety are being made in many different ways. Among these is the provision of bar structures and bodyworks with crumple zones, active seat belts and airbags. These structures have been designed to absorb and spread, by means of controlled deformations, the energy impulse which the vehicle, together with the driver and passengers, are subjected to during a collision. A seat has traditionally been mounted in the vehicle in a fixed manner and has not been designed to absorb and spread the energy impulse or force in any defined way. In order to further improve safety, constructions have therefore recently been proposed in which energy absorbing elements are added to the seat structures; these elements being configured absorb energy in a controlled manner when the seat is subjected to an energy impulse in the event of a collision.
A serious problem in collisions is the risk of neck injuries, also referred to as whiplash injuries to passengers of the crashed vehicle. These injuries can also occur when collisions take place at relatively low speeds and with relatively low energy. The risk of injuries occurring increases when the passenger is not sitting directly against the backrest and headrest. During the course of a rear-end collision, the occupant is flung forwards even if that occupant is wearing a seat belt. When the restrictive limits of the seat belt are reached (the passenger presses against the seat belt and the seat belt becomes taught), then the occupant, in reaction to hitting the limiting seat belt, is flung backward against the backrest and headrest. The risk of injures is increased by the lack of ways to coordinate between these movements of the occupant and the movement of the back rest and the headrest.
Another problem in collisions is the risk of the passenger slipping forwards. This means that during a collision the passenger tends to slip forwards on the seat, and the passenger's knees risk hitting the front structure causing injury. A way of reducing the risk of slipping forwards is described in International Patent Application WO 93/01950 in which the seat structure allows the seat-cushion to move along a controlled, predetermined trajectory which is configured so that the front part of the seat moves upwards and forwards in a front-end collision. This means that the passenger, in order to slip forwards, has to do so along an upward slope. As the passenger moves along the upward slope, the normal force between the passenger's body and the seat is greater than it is in the case where the upward slope is not present. This causes the friction between traveler and the seat to be greater, and therefore the force component in the direction of movement is less. Both of these phenomena contribute to reducing the risk of the passenger slipping forwards. In addition, energy-absorbing members can be mounted on the seat structure and they contribute to the absorption of energy when the seat is moving along the predefined trajectory.
Seat structures like those described in WO 93/01950, however, have the following problems: The seat structure is mounted in a frame construction with milled-out tracks. This construction causes the total weight of the seat structure to be relatively high. Since great efforts are being made to reduce the weight of vehicles in order to achieve better economic operation and reduce impact on the environment, it is not acceptable for parts included in the vehicle to be made heavier than is necessary. In addition, seat structures according to WO 93/01950 have no movement trajectory for cases where the collision occurs from behind in a rear-end impact collision. This means that the risk of neck injuries occurring in rear impact collisions is not benefitted by this type of structure. Another disadvantage of seat structures according to WO 93/01950 is that the backrest does not include any function for increasing adaptability or coordination between the passenger and the backrest in the event of a collision, which among other things reduces the risk of whiplash injuries in a rear impact collision.
In view of the above described deficiencies associated with conventionally designed vehicular carried chair structures, the present invention has been developed. These enhancements and benefits are described in greater detail hereinbelow with respect to several alternative embodiments of the present invention.